Air-driven tuning fork



April 28, 1931. R. H. RANGER 1,802,478

AIR DRIVEN TUNING FORK Filed June 4, 1929 INVENTOR R.H. RANGER BYATTORNE Patented Apr. 28, 1931 UNITED STATES PATENT OFFICE RICHARDHOWLAND RANGER, OF NEWARK, NEW JERSEY, ASSIGNOR T0 RADIO COR- PORATIONOF AMERICA, A CORPORATION OF DELAWARE AIR-DRIVEN TUNING FORK Applicationfiled June 4, 1929. Serial No. 368,404.

The present invention relates broadly to a method and means for drivingtuning forks and the like, and forms a divisional part of my copendingapplication, Serial No. 169,620, filed Feb. 19, 1927.

More specifically, my invention is directed to and relates to a methodand means by which quartz or steel tuning forks, and the like, may bedriven or vibrated by means of an air jet so as to eliminate allelectrical contacts from the drive therefor.

Heretofore, it has been most difficult to drive tunin forks andespecially quartz tuning forks since it was necessary to add pieces ofsteel to a quartz tuning fork in order that the fork might beelectrically driven, and, this addition of steel or other metallicsubstance to the end of the fork tine, it was observed, had a more orless detrimental effect upon the accuracy of the fork itself.

As a principal object of my invention, '1, therefore, sought to producea novel means for controlling tuning forks by means of an air jet.

Still other objects of my invention are to provide in a manner to behereinafter set forth an air means for driving tuning forks and the likewhich is relatively simple in its construction and arrangement of parts,as well as a system which is durable, compact, eflicient in its use,conveniently operated, readily set up, fool-proof, and relativelyinexpensive to install.

The novel features which I believe to be characteristic of my inventionare set forth in the hereinafter appended claims, but the inventionitself, both as to its organization and method of operation togetherwith further objects and advantages thereof, will be best understood bymaking reference to the following specification when read in connectionwith the accompanying drawing, wherein, the single figure thereof is aschematic illustration, partly in section, of an air vibrating means fordriving a tuning fork in accordance with my invention.

Now, to make reference to the above identified drawing. which forms apart of my disclosure, air from any desired source of constantpressure(not shown) may be carried through an air hose 1 to an air chamber 3through any desired type of air inlet, for example, by a tube 5 adaptedto permit the inward passage of air. Branching off from either side ofthe air chamber 3 at points 90 from the inlet of the tube 5 are twoopenings 7 and 9 which open the tines of a tuning fork, generallydesignated 11. Placed against each of the openings 7 and 9 and flushwith them are a pair of cylindrical plug members 13 and 15 respectively,which have their opposite ends 17 and 19 flattened and attached to theends of the tines 21 and 23 respectively of the tuning fork by means ofa screw or some other equivalent means, or which may be, if desired,cast directly as a part of the fork itself. Leading out from the otherend of the air chamber, that is, the end directly opposite the point ofair entrance of the tubular member 5, is a fourth opening or duct 25leading to a tubular member 27, which I shall hereinafter describe as anair resonant column.

The tuning fork 11 may be mounted from its end 29 by any desired andsuitable form of clamping means (not shown), and the tines 21 and 23thereof extend outwardly from the clamping or support means toward theair chamber 3 to the point where the tines are fastened to the plugs 13and 15 which, as above described, rest against the air chamber andthrough the openings of which air which is supplied to the air chamberunder pressure from the source passes out to drive the fork in a mannerto be hereinafter described.

It has been found that the tuning fork, through the attached plugs 13and 15, acts as a bafile on the outlet portions 7 and 9 of the airchamber 3, and as air fills the air chamber, it gradually forces theplugs 13 and 15 outwardly. Upon the outward movement of the fork tines,the plugs 13 and 15 are moved a slight amount away from the air chamberand the air pressure therein is thus released. After the tine of thefork has been moved or forced outwardly, it inherently tends to returnto its original position through its own elasticity and in so doingbrings the plug members 13 and 15 back to their former position againstthe outlet from the air chamber so as to again charge the chamber withair.

Aswillreadily be seen, the charging and discharging of the chamber 3with air supplied through the air inlet tube 1 is a function of thenatural period of vibration of the tuning fork member 11, and in orderto support this vibration, the resonant air column 27 may be adjusted byloosening the support 28 therefor and then moving the slide member 31contained within the resonant air chamber 27, and supported by asupporting bracket 32, for example, either in or out with respect to theair chamber 3 by grasping the knob 33 so as to push the tube 31 into theair chamber or to retract the tube from the resonant air chamber. Bysuch adjustment, the natural period at which the air may fillthe'chamber 3 may be made to substantially correspond to the fork fre-'quency.

It may, therefore, be seen that there is an alternate charging anddischarging action of the air taking place in the air chamber whichtakes place in accordance with the period of vibration of the fork. Thischarging and discharging action gives a good clean cut vibration to thefork, and, by use of the method herein described, it is possible to havean exceedingly low intensity of vibration of the fork, and,naturally,-the lower the vibration intensity, the more constant theperiod of the fork. By means of the air, it is possible to work with amuch less intensity of vibration than is normally possible with-anelectrically driven fork, and it may also be seen, where the rate atwhich the air is permitted to fill the air chamber is made the same asthe period of the fork, that this in itself means accuracy invibrational periods of the fork. Under the above described conditions,theair which is led to the air chamber is under constant pressure, andwhen the air chamber itself is made broadly resonant to the period ofthe tuning fork by suitable adjustment of -the tubular member 33 withinthe tube 27 forming the resonant air column, there is little or nodifliculty in sustaining vibrations of the fork with very low airpressure, which may, for example, be of the order of two pounds persquare inch, although it is to be understood that I do not limit myselfto such a value but other air pressures may be substituted where founddesirable.

Vibrational impulses from the. fork may be utilized in any desirablemanner for synchronizing movable apparatus or for utilizing the airleaving the resonant air column for the purpose of applyng correctiveimpulses upon brakes for motors and the like, as disclosed in my abovenamed copending application of which this forms a divisional part.

Other modifications and changes to the arrangement herein disclosed willat once suggest themselves to those skilled in the art to which theinvention relates, and I, therefore, believe myself to be entitled tomake any and all modifications thereof that fall fairly within thespirit and scope of the hereinafter appended claims.

Having now described my invention, what I claim and desire to secure byLetters Patent is the following:

1. A means for vibrating a tuning fork which comprises a tuning fork, achamber provided with openings adjacent to the tines of said fork, aplug member extending toward and adjacent said opening associated witheach of said tines, and means for forcing air into said chamber, wherebyan air pressure adapted to force said tines outwardly by means of saidplugs is produced within said chamber.

2. A means for vibrating a tuning fork or the like which comprises atuning fork, a resonant air chamber provided with openings adjacent thetines of said fork, a plug member extending toward and adjacent saidopenings associated with each of said tines, and means for forcing airinto said chamber whereby pressure ada ted to force said tines outwardlyby means of said plugs is produced within the said chamber.

3. A system for producing vibration of tuning forks and the like whichincludes a resonant air chamber, means for supplying air at apredetermined pressure to said air chamber, and means associated withsaid air chamber for utilizing the air pressure contfairlied therein forvibrating the said tuning or z.

4. A system for vibrating tuning forks and the like which includes aresonant air chamber having an opening at one end thereof, means forsupplying air at a predetermined pressure to said opening, said chamberalso having openings extending in two directions therefrom atsubstantially right angles to the said air inlet opening, a plug membercarried by each of said tines of said tuning fork and extending withinsaid last named openings, means provided by said air pressure withinsaid chamber for forcing said plugs outwardly therefrom and therebyvibrating said fork, and means opposite said air inlet opening foradjusting the resonant period of said air chamber to substantiallycorrespond to the natural period of vibration of said tuning fork.

RICHARD HOWLAND RANGER,-

